title: Item response theory and structural equation modelling for ordinal data: Describing the relationship between KIDSCREEN and Life-H.
abstract: Both item response theory and structural equation models are useful in the analysis of ordered categorical responses from health assessment questionnaires. We highlight the advantages and disadvantages of the item response theory and structural equation modelling approaches to modelling ordinal data, from within a community health setting. Using data from the SPARCLE project focussing on children with cerebral palsy, this paper investigates the relationship between two ordinal rating scales, the KIDSCREEN, which measures quality-of-life, and Life-H, which measures participation. Practical issues relating to fitting models, such as non-positive definite observed or fitted correlation matrices, and approaches to assessing model fit are discussed. item response theory models allow properties such as the conditional independence of particular domains of a measurement instrument to be assessed. When, as with the SPARCLE data, the latent traits are multidimensional, structural equation models generally provide a much more convenient modelling framework.
authors.affiliation: Department of Mathematics and Statistics, Lancaster University, UK a.titman@lancaster.ac.uk.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Titman
authors.affiliation: Department of Mathematics and Statistics, Lancaster University, UK.
authors.forename: Gillian A
authors.initials: GA
authors.lastname: Lancaster
authors.affiliation: Institute of Health and Society, Newcastle University, UK.
authors.forename: Allan F
authors.initials: AF
authors.lastname: Colver
mesh_terms: D002547:Cerebral Palsy / Q000523:psychology*; D002648:Child; D005260:Female; D006306:Health Surveys / Q000379:methods*; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D011788:Quality of Life; D012984:Software
keywords: cerebral palsy; health assessment; item response theory; ordinal data; structural equation modelling